Process for the oxidation of olefinammonia mixtures to unsaturated nitriles



United States Patent 3,282,982 PROCESS FOR THE OXIDATION OF OLEFTN- AMMONIA MIXTURES TO UNSATURATED NITRILES James L. Callahan, Bedford, Ohio, and Berthold Gertisser,

New York, N.Y., assignors to The Standard Oil Company, Cleveland, Ohio, a corporation of Ohio No Drawing. Original application Oct. 15, 1962, Ser. No. 230,684, now Patent No. 3,200,081, dated Aug. 10, 1965. Divided and this application Jan. 11, 1965, Ser.

6 Claims.

This application is a division of application Serial No. 230,684, filed October 15, 1962, now US. Patent No. 3,200,081, patented August 10, 1965.

This invention relates to the oxidation of olefin-ammonia mixtures to unsaturated nitriles, such as propyleneammonia to acrylonitrile, using oxidation catalyst systems consisting essentially of oxides of antimony and manganese.

US. Patent No. 2,904,580 dated September 15, 1959, describes a catalyst composed of antimony oxide and molybdenum oxide, as antimony molybdate, and indicates its utility in converting propylene to acrylonitrile.

British Patent 864,666 publish-ed April 6, 1961, describes a catalyst composed of an antimony oxide alone or in combination with a molybdenum oxide, a tungsten oxide, a tellurium oxide, a copper oxide, a titanium oxide, or a cobalt oxide. 'Ilhese catalysts are said to be either mixtures of these oxides or oxygen-containing compounds of antimony with the other metal; such as antimony molybdate or molybdenum antimonate. These catalyst systems are said to be useful in the production of unsaturated aldehydes such as acrolein or methacrolein from olefins such as propylene or isobutene and oxygen.

British Patent 876,446 published August 30, 1961, describes catalysts including antimony, oxygen and tin, and said to be either mixtures of antimony oxides with tin oxides, or oxygen-containing compounds of antimony and tin such as tin antimonate. These catalysts are said to be useful in the production of unsaturated aliphatic nitriles such as acrylonitrile from olefins such as propylene, ox ygen and ammonia.

I. THE CATALYST In accordance with the invention, an oxidation catalyst is provided consisting essentially of oxides of antimony and manganese. This catalyst is useful not only in the oxidation of olefins to oxygenated hydrocarbons 3,282,982 Patented Nov. 1, 1966 system will be referred to as a mixture of antimony and manganese oxides, but this is not to be construed as meaning that the catalyst is composed either in whole or in part of these compounds. 7

The proportions of antimony and manganese in the catalyst system may vary widely. The SbzMn atomic ratio can range from about 1:50 to about 99:1. However, optimum activity appears to be obtained at SbzMn atomic ratios within the range from 1:1 to 25: 1.

The catalyst can be employed with-out support, and will display excellent activity. It also can be combined with an inert support, and preferably at least 10% up to about 90% of the supporting compound by weight of the entire composition is employed in this event. Any known support materials can be used, stable underthe reaction conditions to be encountered in the use of the catalyst.

The antimony oxide and manganese oxide can be blended together, or can be formed separately and then blended, or formed separately or together in situ. As starting materials for the antimony oxide component, for example, there can be used any antimony oxide, such as antimony trioxide, antimony tetroxi-de and antimony pentoxide, or mixtures thereof; or a hydrous antimony oxide, metaantimonic acid, orthoantimonic acid or pyroantimonic acid; or a hydrolyzable or decomposable an-timony salt, such as an antimony halide, for example, antimony trichloride, trifluoride or tribromide; antimony pentachloride and antimony pentafiuoride, which is hydrolyzable in water to form the hydrous oxide. Antimony metal can be employed, the hydrous oxide being formed by oxidizing the metal with an oxidizing acid such as nitric acid.

The manganese oxide component can be provided in the form of any manganese oxide, or by precipitation in situ from a soluble manganese salt such as the nitrate, acetate, or a halide such as the chloride. Manganese metal can be used as a starting material, and if antimony metal is also employed, the antimony can be converted to the oxide and manganese to the nitrate simultaneously by oxidation in hot nitric acid. A slurry of hydrous antimony oxide formed in situ from the metal and any other soluble salts are removed by filtration of such as acrolein and the oxidation of olefin-ammonia mixtures to unsaturated nitriles such as acrylonit-rile, but also in the catalytic oxidative dehydrogenation of olefins to diolefins.

The nature of the chemical compounds which compose the catalyst of the invention is not known. The catalyst may be a mixture of antimony oxide or oxides and manganese oxide or oxides. It is also possiblethat the antimony and manganese are combined with the oxygen to form a manganese antimonate. X-ray examination of the catalyst system has indicated the presence of a structurally common phase of the antimony type, composed of antimony oxide, and some form of manganese oxide. Antimony tetroxide has been identified as present. For the purposes of description of the invention, this catalyst the resulting slurry.

It will be apparent from the above that manganous formate, maganous acetate, managanous dibromide, manganous diiodide, manganous dichloride, manganic perchloride, manganic perbromide, manganous difluor-ide, manganic tn'fluoride, manganous nitrate, manganous sulfate, manganic sulfate, maganous thiocyanate, manganous dibasic phosphate, maganous ammonium sulfate, maganese (ous, ic) oxide Mn O manganous oxide, manganous dioxide, manganic oxide, manganese heptaoxide, and manganese trioxide can be employed as the source of the manganese oxide component.

The catalytic activity of the system is enhanced by heating at an elevated temperature. Preferably, the catalyst mixture is dried and heated at a temperature of from about 500 to about 1150 F. preferably at about 700 to 900 F. for from two to twenty-four hours. If activity then is not sufficient, the catalyst can be further heated at a temperature above about 1000 F. but below a temperature deleterious to the catalyst at which it is melted or decomposed, preferably from about 1400 F. to about 1900 F. for from one to forty-eight hours, in the presence of air or oxygen. Usually this limit is not reached before 2000" F. and in some cases, this temperature can be exceeded.

In general, the higher the activation temperature, the less time required to effect activation. The sufficiency of activation at any given set of conditions is ascertained by a spot test of a sample of the material for catalytic ac tivity. Activation is best carried out in an open chamber, permitting circulation of air or oxygen, so that any oxygen consumed can be replaced.

The antimony oxide-manganese oxide catalyst composition of the invention can be defined by the following empirical formula:

where a is l to 99, b is 50 to 1, and c is a number taken to satisfy the average valences of antimony and manganese in the oxidation states in which they exist in the catalyst as defined by the empirical formula above. Thus, the Sb valence may range from 3 to 5 and the Mn valence from 2 to 7.

This catalyst system is useful in the oxidation of olefins to oxygenated compounds, such as aldehydes, in the presence of oxygen, and in the oxidation of olefins to unsaturated nitriles in the presence of oxygen and ammonia. Both nitriles and aldehydes can be produced simultaneously using process conditions Within the overlapping ranges for these reactions, as set forth in detail below. The term oxidation as used in this specification and claims encompasses the oxidation to aldehydes and to nitriles, both of which require oxygen as a reactant.

II. OXIDATION OF OLEFINS TO NITRILES The reactants used propylene, or isobutyleue, or I11lX- tures thereof, and oxygen, plus ammonia.

In its preferred aspect, the process comprises contacting a mixture comprising propylene or isobutylene, ammonia and oxygen with the catalyst at an elevated temperature and at atmospheric or near atmospheric pressure.

Any source of oxygen may be employed in this process. For economic reasons, however, it is preferred that air be employed as the source of oxygen. From a purely technical viewpoint, relatively pure molecular oxygen will give equivalent results. The molar ratio of oxygen to the olefin in the feed to the reaction vessel should be in the range of :521 to 4:1 and a ratio of about 1:1 to 3:1 is preferred.

Low molecular weight saturated hydrocarbons do not appear to influence the reaction to an appreciable degree, and these materials can be present. Consequently, the addition of saturated hydrocarbons to the feed to the reaction is contemplated within the scope of this invention. Likewise, diluents such as nitrogen and the oxides of carbon may be present in the reaction mixture Without deleterious effect.

The molar ratio of ammonia to olefin in the feed to the reaction may vary between about 0.05:1 to 5:1. There is no real upper limit for the ammonia-olefin ratio, but there is generally no reason to exceed the 5:1 ratio. At ammonia-olefin ratios appreciably less than the stoichiometric ratio of 1:1, various amounts of oxygenated derivatives of the olefin will be formed.

Significant amounts of unsaturated aldehydcs as well as nitriles will be obtained at ammonia-olefin ratios substantially below 1: l, i.e., in the range of 0.15:1 to 0.75:1. Outside the upper limit of this range only insignificant amounts of aldehydcs will be produced, and only very small amounts of nitriles will be produced at ammoniaolefin ratios below the lower limit of this range. It is 4 fortuitous that within the ammonia-olefin range stated, maximum utilization of ammonia is obtained and this is highly desirable. It is generally possible to recycle any unreacted olefin and unconverted ammonia.

A particularly surprising aspect of this invention is the effect of water on the course of the reaction. We have found that in many cases water in the mixture fed to the reaction vessel improves the selectivity of the reaction and yield of nitrile. However, reactions not including water in the feed are not to be excluded from this invention, inasmuch as water is formed in the course of the reaction.

In general, the molar ratio of added water to olefin, when water is added, is at least about 0.25:1. Ratios on the order of 1:1 to 311 are particularly desirable, but higher ratios may be employed, i.e., up to about 10:1.

The reaction is carried out at a temperature within the range from about 550 to 1100 F. The preferred temperature range is from about 800 to 1000 F.

The pressure at which reaction is conducted is also an important variable, and the reaction should be carried out at about atmospheric or slightly above atmospheric (2 to 3 atmospheres) pressure. In general, high pressures, i.e., about 250 p.s.i.g., are not suitable, since higher pressures tend .to favor the formation of undesirable by-pr'oducts.

The apparent contact time is not critical, and contact time in the range of from 0.1 to about 50 seconds may be employed. The optimum contact time will, of course, vary, depending upon the olefin being treated, but in general, a contact time of from 1 to 15 seconds is pre-. ferred.

In general, any apparatus of the type suitable for carry-. ing out oxidation reactions in the vapor phase may be employed in the execution of this process. The process may be conducted either continuously or intermittently. The catalyst bed may be a fixed bed employing a large particulate or pelleted catalyst or, in the alternative, a so-called fluidized bed of catalyst may be employed.

The reactor may be brought to the reaction temperature before or after the introduction of the reaction feed mixture; However, in a large scale operation, it is preferred to carry out the process in a continuous manner, and in such a system the recirculation of the unreacted olefin is contemplated. Periodic regeneration or reactivation of the catalyst is also contemplated, and this may be accomplished, for example, by contacting the catalyst with air at an elevated temperature.

The products of the reaction may be recovered by any of the methods known to those skilled in the art. One such method involves. scrubbing the efiiuent gases from the reactor with cold water or an appropriate solvent oxidizing agent in this process, the resulting product.

mixture remaining after the removal of the nitriles may be treated to remove carbon dioxide with the remainder of the mixture containing the unreacted propylene and oxygen being recycled through the reactor. In the case Where air is employed as the oxidizing agent in lieu of molecular oxygen, the residual product after separation of the nitriles and other carbonyl products may be scrubbed with a non-polar solvent, e.g., a hydrocarbon fraction, in order to recover unreacted propylene and in this case the remaining gases may be discarded. The addition of a suitable inhibitor to prevent polymerization of the unsaturated products during the recovery steps is also contemplated.

T e following examples, in the opinion of the inven- The efficiency of the scrubbing operators, represent preferred embodiments of the catalyst system of the invention, and of the processes of oxidation of olefins therewith.

Example 1 was then activated by heating in a muffie furnace open to the atmosphere at 1400 F. for 8 hours.

This catalyst was employed in a bench scale reactor having a capacity of approximately 100 ml. of catalyst, in a fixed bed, for the conversion of propylene to acrylonitrile. The feed gases were metered by rotameters, and water was fed by means of a Sigma motor pump through capillary copper tubing. In the test, a 90 ml. catalyst charge was used. The molar ratios of propylene/ammonia/ air/ nitrogen/ water (for acrylonitrile) are given in Table I, together with the apparent contact time and the reaction temperature and yield.

TABLE I Feed Molar Apparent Oon- Percent Conversion per Pass Example No. Ratio O INH I tact Time Temperature, Total All'lNz/HgO (seconds) F.

Acrylonitrile Acetonitrile 1/l. 5/12/4/1 4 870 70. 7 57. 2 3. 3 III. 5/12/4/1 3. 5 900-030 69. 0 49. 6 3. 5 1/1. 5/12/4/1 4 860-870 67. 0 51. 6 5. 4

nitrate. Twenty-eight percent ammonium hydroxide was added until a pH of 7.2 was reached. The slurry was filtered, and washed with 300 cc. of 2.5% ammonium hydroxide solution, divided into three equal portions. Air was drawn through the filter cake for one hour following the last washing. The catalyst was dried overnight at 120 C., calcined at 800 F. overnight, and heattreated overnight at 1400 F. in a mufile furnace open to the atmosphere.

The activity of this catalyst in the conversion of propylene to acrylonitrile was determined using a micro reactor composed of a feed induction system, a molten salt bath furnace reactor, sampling valve and vapor phase chromatograph. The reactor was placed in the salt bath furnace, and connected with the feed induction system and sampling device. The reaction was carried out at a temperature of approximately 880 F. using a catalyst charge of 9.6 g. A gas mixture containing propylene/ ammonia/air in a volume ratio of 1 to 1 to 12 was passed over the catalyst at an apparent contact time of three seconds. 48.6% of the propylene feed was converted to acrylonitrile, and the remainder to acetonitrile and carbon oxides.

Example 2 The catalyst of Example 1 (37.9 grams) was mixed with 12.7 g. of silicon carbide obtained by grinding silicon carbide pellets. Suflicient water was added to form a smooth paste. This was dried and calcined overnight at 800 F. 7.7 g. of this catalyst was employed in the reactor of Example 1 under the same conditions. 61.9% of the propylene feed was converted to acrylonitrile, to acetonitrile, and the remainder to carbon oxides.

Examples 3 to 7 One hunderd grams of antimony metal was oxidized by heating in 420 cc. of concentrated nitric acid until evolution of nitrogen oxides had ceased. The suspension of antimony oxide was added to 218 g. of a 50% solution of manganous nitrate. Next, 340 cc. of 28% ammonium hydroxide solution was added with vigorous stirring, and the slurry filtered. The filter cake was washed with 300 cc. of water divided into three equal portions. Air was drawn through the filter cake for 10 minutes. The material was then dried at 120 C. The resulting powder was passed through a 35 mesh sleeve, pelleted, and calcined at 800 F. overnight. The catalyst Excellent per pass conversions to acrylonitrile are thus obtainable, using this catalyst system.

We claim:

1. A process for the oxidation of propylene and isobutylene to acrylonitrile and methacrylonitrile, respectively, which comprises the step of contacting in the vapor phase at a temperature within the range from about 550 to about 1100 F. a mixture of ammonia, oxygen and an olefin selected from the group consisting of propylene and isobutylene and mixtures thereof, in a molar ratio of olefin to ammonia within the range from a bout 1:05 to about 1:5, and a molar ratio of oxygen to olefin within the range from about 0:5 :1 to about 4:1, in the presence of a catalyst composition consisting essentially of an active catalytic oxide complex of antimony and manganese as an essential catalytic ingredient, the SbzMn atomic ratio being within the range from about 1:50 to about 99:1, said complex being formed by heating the mixed oxides of antimony and manganese in the presence of oxygen at an elevated tempearture above 500 F. but 'below their melting point for a time sufficient to form said active catalytic oxide complex of antimony and manganese.

2. The process of claim 1, in which the SbzMn atomic ratio in the catalyst is within the range from 1:1 to 25: 1.

3. The process of claim 1, in which the catalyst composition is supported on an inert support.

4. The process of claim 1 in which the molar ratio of oxygen to olefin is from about 1:1 to about 3:1.

5. The process of claim 1 which comprises feeding water in the olefin-ammonia-oxygen mixture in a ratio of water to olefin within the range from about 0.25:1 to about 10:1.

6. The process of claim 1 in which the reaction is carried out at a pressure above atmospheric pressure up to about 250 p.s.i.g.

References Cited by the Examiner UNITED STATES PATENTS 2,621,204 12/ 1952 Maclean et al 260465.3 2,776,316 1/ 1957 Baldwin 260-604 2,941,007 6/ 1960 Callahan 260-604 3,009,943 11/1961 Hadley et al. 260--465.3

CHARLES B. PARKER, Primary Examiner.

UNITED STATES PATENT OFFICE Certificate Patented November 1, 1966 James L. Callahan and Berthold Gertisser Application having been made jointly by James L. Callahan and Berthold Gertisser, the inventors named in the patent above identified, and The Standard Oil Compan of Cleveland, Ohio, a corporation of Ohio, 1; e assignee, for the issuance of a certi cate under the provisions oii Title 35, Section 256 of the United States Code, delehing the Patent N 0. 3,282,982

EDWIN L. REYNOLDS, First Assistant Uommz'ssioner of Patents. 

1. A PROCESS FOR THE OSICATION OF PROPYLENE AND ISOBUTYLENE TO ACRYLONITRILE AND METHACRYLONITRIDE, RESPECTIVELY, WHICH COMPRISES THE STEP OF CONTACTING IN THE VAPOR PHASE AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 550 TO ABOUT 1100*F. A MIXTURE OF AMMONIA, OXYGEN AND AN OLEFIN SELECTED FROM THE GROUP CONSISTING OF PROPYLENE AND ISOBUTYLENE AND MIXTURE THEREOF, IN A MOLAR RATIO OF OLEFIN TO AMMONIA WITHIN THE RANGE FROM A BOUT 1:05 TO ABOUT 1:5, AND A MOLAR RATIO OF OXYGEN TO OLEFIN WITHIN THE RANGE FROM ABOUT 0:5:1 TO ABOUT 4:1, IN THE PRESENCE OF A CATALYST COMPOSITION CONSISTING ESSENTIALLY OF AN ACTIVE CATALYTIC OXIDE COMPLEX OF ANTIMONY AND MANGENESE AS AN ESSENTIALLY CATALYTIC INGREDIENT, THE SB:MN ATOMIC RATIO BEING WITHIN THE RANGE FROM ABOUT 1:50 TO ABOUT 99:1, AND COMPLEX BEING FORMED BY HEATING THE MIXED OXIDES OF ANTIMONY AND MANGANESE IN THE PRESENCE OF OXYGEN AT AN ELEVATED TEMPERATURE ABOVE 500*F. BUT BELOW THE MELTING POINT FOR A TIME SUFFICIENT TO FORM SAID ACTIVE CATALYTIC OXIDE COMPLES OF ANTIMONY AND MANGANESE. 